The present invention relates to a system for supplying a coating liquid to various substrates, such as reticle substrates for photomasks, semiconductor wafers, or glass substrates for liquid crystal displays, to form a liquid film by the coating liquid.
In a process for producing semiconductor devices and LCDs, a resist processing on a substrate to be processed is carried out by a technique called photolithography. In this processing, an exposure processing is carried out using a reticle substrate on which a predetermined mask pattern is formed. The formation of the mask pattern on the surface of the reticle substrate is carried out by a series of processes for applying a predetermined chemical (coating liquid) on the surface of a glass substrate to form a liquid film, and thereafter, exposing the liquid film to carry out a development to obtain a desired pattern.
As a conventional method for forming the above described liquid film, there has been adopted the spin coating method for holding a substrate in a horizontal state and rotating the substrate about a vertical axis and for supplying a coating liquid toward the center of the substrate from top to diffuse the coating liquid over the whole surface of the substrate by centrifugal force. However, in this method, there is a problem in that the periphery of the substrate easily becomes dirty since the coating liquid extends outwards, so that particles are easily produced from the coating liquid adhering to the peripheral portion. If particles adhere to the reticle substrate, the shadow of the particles becomes the shape of a circuit pattern as it is, so that it is required to avoid the adhesion of particles. As this measure, for a reticle substrate 11 having a zinc oxide layer 12 and a coating liquid layer 13 for forming a mask pattern as shown in FIG. 20, it is considered that it is effective to expose zinc oxide at the peripheral portion 14 of the substrate to be grounded, for example, in order to prevent the substrate from being charged during exposure by electron beams. However, the grounding method can not be adopted since the coating film is formed on the whole surface of the substrate in the case of the spin coating method.
Therefore, the inventor has studied that a coating device shown in FIG. 21 is used for carrying out a coating process. In the figure, reference number 11 denotes a rectangular reticle substrate which is horizontally held by a substrate holding portion (not shown) movable in Y directions. Above the reticle substrate 11, there are provided a plate 16 formed with a slit 15 extending in X directions, and a nozzle portion 17 for supplying a mask pattern forming coating liquid to the reticle substrate 11, which is arranged below the plate 16, via the slit 15. Reference numbers 18a and 18b are a pair of shutters which are provided on both sides of a slit 14 above the plate 16 and which have, e.g., a tray shape, so as to be capable of recovering the coating liquid dropping from the nozzle portion 17 moving above the shutters.
During a coating process, the nozzle portion 17 is reciprocated (scanned) in X direction from above the shutter 18a to above the shutter 18b, and the reticle substrate 11 arranged below the nozzle portion 17 is intermittent-fed in Y directions, so that the lines of the coating liquid having a length corresponding to the slit 15 are closely arranged on the surface of the reticle substrate 11 as shown in FIG. 22. The length of the slit 15 is determined so as to prevent the coating liquid from being supplied to the periphery of the reticle substrate 11 and so as to expose the underlaying zinc oxide. The coating liquid which should be originally coated on the periphery of the reticle substrate is recovered by the shutters 18a and 18b. 
In the method for scanning the nozzle portion to coat the coating liquid, the reticle substrate is not rotated, so that there are advantages in that it is possible to inhibit the peripheral portion from being contaminated, that it is possible to apply the coating liquid on the whole surface of the reticle substrate while exposing zinc oxide, and that it is possible to make good use of the coating liquid. However, during the supply of the coating liquid, there are some cases where part of the coating liquid hitting on the surface of the reticle substrate and the top face (liquid receiving face) and side faces (the faces of the shutters 18a and 18b facing each other) of the shutters splashes to fly off as mist, which becomes particles adhering to the surface of the reticle substrate. Particularly on the side face portions of the shutters on which the coating liquid first hits during the scanning of the nozzle portion, mist is easily produced by the shock of the hitting of the coating liquid. In addition, the downward flow of clean air is formed in the coating device, so that there is also a problem in that the mist produced around the shutters, together with the downward flow, easily flows toward the reticle substrate via the slit.
In addition, the thickness of the thin film of the coating liquid formed on the surface of the shutters gradually increases by repeating the coating process, and a part thereof is peeled off to cause particles. Therefore, the shutters must be removed in predetermined timing. For example, the shutters must be replaced with cleaned shutters, and the removed shutters must be cleaned, so that there is a problem in that work is troublesome. In addition, it is required to ensure a space required to clean the shutters, so that there is also a problem in that the system increase in size.
The present invention has been made in the circumstances, and it is an object of the present invention to provide a technique for scanning a nozzle portion in lateral directions and moving a substrate in longitudinal directions to inhibit particles from adhering to the surface of the substrate in a system for forming a liquid film of a coating liquid on the surface of the substrate. It is another object of the present invention to provide a technique for improving the yields of a coating film formed on the surface of a substrate.
According to one aspect of the present invention, a coating film forming system comprises: a substrate holding portion for horizontally holding a substrate; a first driving part for moving the substrate holding part in longitudinal directions; a nozzle portion, provided so as to face the substrate held on the substrate holding portion, for discharging a coating liquid to the substrate; a second driving part for moving the nozzle portion in lateral directions; a plate which has a slit being open so as to have a width corresponding to a lateral width of a coating region of the substrate and which is provided between the nozzle portion and the substrate; and a suction mechanism for sucking a suspended matter over a range corresponding to the width of the slit via a suction port which is provided in the vicinity of the slit, wherein the nozzle portion is moved in the lateral directions to linearly apply the coating liquid in linear coating regions on the substrate via the slit, and thereafter, the substrate is intermittently moved so as to closely arrange the linear coating regions in the longitudinal directions, to form a coating film.
With this construction, fine suspended matters, such as the mist of the coating liquid flying during a coating process, can be recovered by the slit, so that it is difficult to contaminate the substrate when the coating film is formed. If the suction port is provided above the plate in the vicinity of the slit, fine suspended matters, such as the mist of the coating liquid, can be recovered by the slit before flowing into the slit, so that it is difficult to contaminate the substrate when the coating film is formed. If the suction ports are provided above and below the plate in the vicinity of the slit, fine suspended matters, such as the mist of the coating liquid, can be surely recovered on both sides of upper and lower sides of the plate. The mist sucked by the suction port(s) includes mist produced by the discharge of the coating liquid from the nozzle portion, mist produced by the collision of the coating liquid with the shutter, and mist rebounding from the substrate. The mist directly discharged from the nozzle portion, and the mist produced by the collision of the coating liquid with the shutter mainly exist above the plate, and the mist produced by the collision of the coating liquid with the substrate mainly exists below the plate.
Particularly, in order to effectively recover the mist of the coating liquid of suspended matters, the suction port preferably has a width corresponding to a movable range of the nozzle portion in the lateral directions.
According to another aspect of the present invention, a coating film forming system comprises: a substrate holding portion for horizontally holding a substrate; a first driving part for moving the substrate holding part in longitudinal directions; a nozzle portion, provided so as to face the substrate held on the substrate holding portion, for discharging a coating liquid to the substrate; a second driving part for moving the nozzle portion in lateral directions; a plate which has a slit being open so as to have a width corresponding to a lateral width of a coating region of the substrate and which is provided between the nozzle portion and the substrate; and a shutter, provided on both ends of the slit, for receiving the coating liquid from the nozzle portion; a shock eliminating portion, provided on an end portion of a liquid receiving surface of the shutter on the side of the slit, for eliminating the shock of the coating liquid, which first hits on the shutter, to decrease the amount of occurrence of mist, when the nozzle portion moves above the shutter beyond the coating region of the substrate, wherein the nozzle portion is moved in the lateral directions to linearly apply the coating liquid in linear coating regions on the substrate via the slit, and thereafter, the substrate is intermittently moved so as to closely arrange the linear coating regions in the longitudinal directions, to form a coating film.
The shock eliminating portion is preferably formed so as to have an end portion facing in a lateral direction on the side of the slit on the liquid receiving surface and so as to protrude at an acute angle, and has a porous structure, and suction is preferably carried out in the shock eliminating portion. With this construction, it is possible to eliminate the shock of the coating liquid colliding with the shutter to remarkably reduce the occurrence of mist.
In addition to the above described construction, if the liquid receiving surface of the shutter is inclined with respect to the horizontally held substrate, and if a solvent supply port for supplying a solvent for washing the coating liquid adhering to the liquid receiving surface is formed in a region above the shock eliminating portion on the liquid receiving surface, and if a suction port for sucking the solvent is formed in a region below the shock eliminating portion on the liquid receiving surface, it is possible to prevent the coating liquid adhering to the liquid receiving surface from being solidified and suspended as particles. In order to more effectively prevent mist from flying, the suction port is preferably provided on the front side of the inclined liquid receiving surface, and the portion in the vicinity of the shutter and slit is preferably detachable.
According to a further aspect of the present invention, a coating film forming system comprises: a housing which defines a space for processing a substrate; a substrate holding portion, provided in the housing, for horizontally holding the substrate; a first driving part for moving the substrate holding part in longitudinal directions; a nozzle portion, provided in the housing so as to face the substrate held on the substrate holding portion, for discharging a coating liquid to the substrate; a second driving part for moving the nozzle portion in lateral directions; a filter unit for supplying clean air into the housing; a plate for dividing the interior of the housing into an upper space including the filter unit and the nozzle portion, and a lower space including the substrate holding portion and the substrate held on the substrate holding portion; a slit which is formed in the plate so as to have a width corresponding to a lateral width of a coating region of the substrate so that the coating liquid supplied from the nozzle portion is applied on the coating region of the substrate; one or more vent holes, which are formed in the plate in a region other than a movable region of the substrate in the lower space when the plate is viewed from top, so that air supplied from the filter unit flows into the lower space; and exhaust means for exhausting air from the lower space, wherein the nozzle portion is moved in the lateral directions to linearly apply the coating liquid in linear coating regions on the substrate via the slit, and thereafter, the substrate is intermittently moved so as to closely arrange the linear coating regions in the longitudinal directions, to form a coating film.
With this construction, it is possible to prevent a downward flow from concentrating on the slit in the upper space, and air flows so as to avoid the substrate in the lower space, so that it is difficult for mist to be directed to a reticle substrate R even if the mist is produced in the upper space. In order to prevent the air flow from remaining in the housing and in order to uniformly carry out cleaning, the flow rate of supply air in the filter unit is preferably coincident with the total amount of the flow rate of exhaust air in the housing.